The area of contact between a moving load transfer device such as the wheels or tracks of military vehicles and the surface over which such vehicles move is often needed by design engineers for such purposes as evaluating mobility potential or for determining appropriate adjustment to the load transfer devices. For these purposes both the total area of contact as well as the shape of the contact area are needed. The total area in conjunction with the gross weight of the vehicle would yield the pressure or load per unit area which is important for example in determining whether the vehicle might safely cross a bridge of known capacity. The shape of the contact area would have a bearing on the traction to be expected from different types of ground surfaces. Also, the load per unit area is important for evaluating the rate of wear of such things as tracks and tires.
In the past, measurement of wheel and track loading on supporting structures or on the ground has been accomplished by footprint techniques wherein a print of the outline of the area of contact is made on paper laid on the ground and driven over. Planimeter type devices can then be used to measure the area of the so-called footprint. Also, automatic techniques have been developed for calculating the contact area of the footprint and digitally displaying the results. However the acquisition of the print has remained a tedious and time consuming task. Further, the inaccuracy of this technique means that several prints must be made to assure confidence in the results.
The present invention completely automates such measurements by providing an array of load sensors disposed in a matrix and arranged so that the vehicle to be tested is driven over the matrix. The pressure of the wheels and/or tracks of the vehicle will actuate a number of the load sensors. The array is scanned to determine the number and positions of the actuated load sensors and this information is used to determine the total area of contact as well as the shape thereof. Further, by adjusting the operating threshold of the load sensors, shape and area information can be determined for go-no go requirements.